The present invention is directed to an improved low-voltage vacuum switching device and operating mechanism which is typically used as an electrolytic cell shorting assembly. Such a vacuum switch and operating mechanism is described in U.S. Pat. No. 4,216,359 filed June 13, 1978 entitled "Low-Voltage Vacuum Switch And Operating Mechanism", owned by the assignee of the present invention. This earlier switch and operating mechanism has found significant application as an electrical shunting switch assembly for use with high current carrying electrolytic cells, as a parallel shunt across the terminals of the cell. The switch has a very compact physical profile and short axial contact travel distance. The switch is operated, i.e. opened and closed by means of a small axial movement which is produced by translating a rotational operating shift motion via an eccentric cam to a reciprocating connecting link which acts upon one end of the switch. The switch and operating assembly is a contact, rugged design for use in low-voltage, high-current, severe environment applications.
In the prior switch assembly a plurality of electrically parallel vacuum switches are operated from a common rotating shaft. Individual eccentric cam means are mounted on the shaft and connected to reciprocatable linking means to operate the individual switches. It is generally desired to open and close the switches as nearly simultaneously as possible. When the linking means have some lateral movement capability which can cock the switch contacts, it is difficult to ensure simultaneous contact operation for the plurality of switches. The eccentric cam means is configured so that rotation through a specific angle, i.e. the opening angle, will simultaneously operate the paralleled switches. Any variable lateral movement of the linking means relative to the respective switches makes the setting and selection of the opening angle more difficult.
The switch assembly of the present invention is either permanently connected across the cell terminal, or may be a portable assembly which can be connected and disconnected as a shunt across an individual cell. The cell terminals carry currents of terms of thousands of amperes and significant thermal heating and expansion of these conductors can be expected. When the switch assembly is connected to such thermally affected conductors, and the linking means has lateral movement capability there can be switch contact cocking and accidental switch contact closing.